/Engine/Source/Runtime/Core/Public/Math/UnrealMathUtility.h
This is a version of VRandCone that handles "squished" cones, i.e. with different angle limits in the Y and Z axes. Assumes world Y and Z, although this could be extended to handle arbitrary rotations.
static FVector VRandCone ( FVector const & Dir, float HorizontalConeHalfAngleRad, float VerticalConeHalfAngleRad )